Linear alpha-olefins are important substances which are used for comonomers, detergents, lubricants, plasticizers, etc., and are widely used for commercial purposes. In particular, 1-hexene and 1-octene are frequently used as comonomers for controlling the density of polyethylene in the preparation process of linear low-density polyethylene (LLDPE).
The conventional processes for preparing LLDPE include copolymerizing ethylene with alpha-olefins, for example a comonomer such as 1-hexene or 1-octene, in order to control the density of the polyethylene by forming branches to the polymer backbone. In order to increase the content of comonomers such as 1-hexene, 1-octene, or the like in LLDPE to be synthesized, there was a problem that the production costs increase. Thus, various studies regarding a method for providing the comonomer in a more economical and easy manner have been performed.
The existing commercial processes for preparing 1-hexene or 1-octene may include a SHOP process by Shell Chemical, a Ziegler Process by Chevron Philips, and the like. Using these processes, an alpha-olefin having 4 to 20 carbon atoms can be produced.
Specifically, a catalyst for ethylene oligomerization which includes an organic ligand compound containing a transition metal such as chromium, etc., any one element of phosphorus, arsenic, and antimony, and nitrogen has been known in the art.
Since the alpha-olefin has different application fields or market sizes depending on its type, a technique capable of selectively producing a certain type of olefin is commercially very important. Recently, studies regarding catalyst technology utilizing a transition metal such as chromium to prepare 1-hexene or 1-octene with high selectivity through selective ethylene oligomerization or multimerization have been frequently performed.
Thus, there is a need to develop a process capable of securing high activity and high selectivity for a long period of time in current reaction procedures and oligomerizing olefin monomers in a more economical and easy manner.